One consequence of the change in the user interface between versions 1 and 2 was a loss
of certain features, and some flexibility in specifying input
parameters. Examples include pipelined models and variable gas
density. This sacrifice was deemed acceptable in the interests of streamlined
and simplified execution, and because these features were not often
used (as far as we know). In an effort to preserve these
features in some form for dedicated users we also provide the
capablility to call XSTAR as a fortran subroutine, which allows
the user flexibility in specifying geometry, spectrum and density.
This is described in Chapter 14.